on my 1982 I installed dougs sidepipe headers few weeks ago, have try retorqueing bolts down a number of times with no luck still have one leak on each side, used copper gaskets any suggestions?

 

Is the header flange true?

Studs will give a much better/more even torque than bolts.

 

I recommend a set of Pearcy's Seal 4 Good Dead Soft Aluminum header gaskets. These work for me every time.

 

No gasket ... just hi-temp RTV

 

Some flanges are so thick that they have absolutely no "give" to them. If the flange is warped, that compounds the problem.

An old trick to get some flexibility in the flange is to remove the header just an inch or so. Using a bare hacksaw blade (wearing a glove) cut a "kerf" at two locations on the backside of the flange: between cyl 1 & 3 and also 5 & 7. A kerf does not cut very deep, but just enough to allow the flange to bend and seal better.
Add Percys aluminum gaskets like mentioned above. Then kerf the other header the same way. The kerf will be invisible after its torqued.

Also, when torqueing the bolts its common practice to start the bolts on each end. But final tightening should start in the middle, working your way to the ends.

 

Had a similar issue with a 401 AMC motor I built for my CJ. Couldn't figure it out because the Thorley Tri Y's had fit up fine and I had ran them for a while. The Hedman's flange was a little different, nice heavy flange. I finally rolled up under the jeep and looked from below and found some casting flash on the heads was interfering with the flange. Die grinder and about 10 minutes took care of that problem and they fitted up and sealed well with a copper gasket.

May or may not be relevant with yours but.......

 

I've had good luck with either the dead soft aluminum and the copper header gaskets. But I always put high temp RTV on both sides of the gasket, let it set up a bit and then bolt the header on. Then let it sit overnight? and no leaks.

 

Do yourself a favor and buy 2 sets of the blue Felpro header gaskets that are about $15 per set ($30 for both), take some some red high temp RTV sealant and seal 2 of the gaskets together using a a vise clamp to hold them together, and after they dry, 2 gaskets per side, install them.. I have done this technique on 3 different sets of headers that I could not get to seal with ANY gasket, including Percy's, aluminum/copper, etc NONE of them would seal a warped header, NONE! but the double gasket trick will. You can also try buying a set of Mr gasket, extra thick ultra seal header gaskets, and see if they will work, But I have not tried them and do not know if they will seal a bad warp?

The beauty of the above ^^^ technique is that you do not have to remove the warped header to seal the issue.....you just remove the old header gasket and install the double header gasket and the leak will be sealed...It works with minimal work and permenently...never had a leak after . I have done this technique 2X's on the 78 C3 with 2 different headers AND badly warped BBK Shorty Headers on my 94 mustang GT (nothing will solve the BBK Shorty leak, I mean, NOTHING). The double gasket trick finally solved the leak...I could not believe that it was the only gasket trick to work.....or gasket of any make, material, etc.....

 

Before I discovered the Pearcy's I always doubled up the cheap Felpro's but for me the Pearcy's Dead Soft have always worked and are re useable. My neighbor always RTV's his headers without gaskets but what a mess it is when he needs to remove a header.

 

This!